Lotus and butterfly yoga positions are essentially sitting positions on the floor with the legs crossed, often on a thin seat, which may be referred to as a block or support or cushion.
The presently available floor seats, blocks, supports, or cushions fail to adequately conform to and provide proper separate support for the separate areas of the coccyx or tailbone, the pelvic floor or pelvic diaphragm, and the sitting bones or ischial tuberosities.
Many people practice yoga in a yoga studio located outside of their homes or offices. Yoga studios often have large groups of people practicing simultaneously. A person's practice of yoga is most likely to involve both sitting and non-sitting positions. Therefore, easy transportability and movability of any yoga seat, to and from the studio, and within the studio, are desirable features. For yoga studios, the ability to easily and conveniently store several yoga seats away and then access them again throughout the day is an additional desirable feature.
Apart from the practice of yoga, there are other circumstances where people regularly sit on the floor, such as in certain schools, institutions, and cultural traditions. The performance of certain vocational or avocational manufacturing, repair, or artistic procedures requires persons sitting on the floor. The performance of some observances of faith require persons sitting on the floor. Proper support, encouragement of proper posture, and convenient transport and storage of floor seats is desirable for those uses as well.
Ordinarily, many people sit with more or less slouched postures. Sitting in this way causes the lower spine to curve convexly with the consequence of causing an increase in the convex curve of the middle part of the back, and the head to jut forwards causing potential injury along the length of the spine, especially in the lower back and neck areas. Yoga sitting positions encourage the spine to adopt an upright posture, so that the head is balanced directly above the pelvis and the spine curved normally, that is concavely in the lower back, convexly in the middle back, and concavely in the neck. The pelvis should be in neutral alignment which promotes the ability to sit with the correct concavity of the lower spine.
Much of an individual's weight in sitting is transferred to the seat supporting him/her via the sitting bones of the pelvis. These are the lowermost extensions of the pelvis. Muscle surrounding the pelvis also transfers weight to the seat.
Pubic bones extend up and forwards from the sitting bones. Support from the seat to the pubic bones can aid good/correct posture/postural-alignment.
Depending on the shape of the seat, more or less weight is transferred by muscle and possibly fat to the coccyx, which is joined with the lower part of the sacrum. The upper part of the sacrum is joined with the lower spine. The sacrum is also joined with the pelvis by sacroiliac joints. Pressure from below on the coccyx and sacrum can disturb posture, causing undesirable torsional loading of the spine.
In yoga positions, and it other circumstances of sitting on the floor, the ability to place the heels of one's feet sufficiently close to the area of the sitting bones, pelvic floor, and pubic bone, is important, and even determinative of achieving a proper, comfortable, sustainable posture. Therefore, any seat structure impeding proper and optimal placement of one's feet works against achievement of an optimal floor-sitting position, and removal of such impediment is a beneficial element allowing achievement of a proper posture.
In most individuals, sitting on a flat surface encourages posterior pelvic tilt and an undesirable flattening of the natural lumbar lordosis or even a reversal of this curve. Sitting on a flat surface generally promotes posterior pelvic tilt forcing the lumbar spine into a flattened position as opposed to the desirable flexion, convex position. But sitting on a somewhat forward-inclined surface promotes a neutral alignment of the pelvis, that is neither tilted anteriorly nor posteriorly. As a consequence, this neutral alignment of the pelvis promotes optimal length and alignment of the spine where the three primary curves of the spine are in place—that is the backward facing curves in the lumbar (low back) and cervical (neck) areas and forward facing curve in the thoracic (mid back).
There is a need for a floor seat that will properly support both the sitting bones and the pelvic floor, while avoiding pressure on the coccyx, allowing for proper placement of the feet, and encouraging proper posture. Presently known seats fail in one or more of these areas.
US patent application No 2012/0124749 teaches “A meditation seating cushion. The seating cushion may comprise a first cushion portion, a second cushion portion separate from the first cushion portion, and a strap connecting the first and second cushion portions together. A single seating cushion portion has a substantially planar bottom surface and a substantially semi-cylindrical top surface. The cushion portions are used for disposition on a support surface such as a floor or mat, each cushion portion being underneath one of the user's buttocks, for seating the user so as to avoid imposing stress on that region of the user's bottom including the anus, perineum, and vagina or scrotum.” There is no pelvic-floor support in this device.
U.S. Pat. No. 4,673,216 teaches “A seat for persons using the cross-legged “lotus” sitting position, characterized by a substantially horseshoe-shaped support with top and bottom surfaces and with a broad central portion for supporting the buttocks, and comprised of a pair of bilaterally symmetrical and divergent sections with piers extending forwardly establishing a space therebetween to lower and to position both feet and folded lower legs with the buttocks raised for comfort; a unit to be used at floor level or raised by and/or incorporated in a chair or the like.” Whilst this seat provides pelvic-floor support, it can be expected to exert pressure on the coccyx. Further, I believe that uniform thickness of the piers discourages upright posture, at least without undesirable spine curvature.
In some circumstances, such as in cold or hot environments, strongly vibrating environments, or where separate insulating floor mats are not available, it is also desirable to provide thermal or vibrational insulation in a floor seat, to block or attenuate any effects on the seated person.